A US judge has sentenced former key White House official Lewis "Scooter" Libby to 30 months in prison. He remains free pending an appeal hearing.

Libby was found guilty of obstruction of justice and perjury in March over the investigation into the unmasking of CIA officer Valerie Plame.

Libby was the former chief of staff to Vice-President Dick Cheney.

Nobody has ever been charged with the offence of leaking the name of Ms Plame whose husband criticised the Iraq war.

President George W Bush feels "terrible for the family, especially for his wife and kids," said White House spokeswoman Dana Perino.

'The truth matters'

Vice-President Cheney said his former aide's prison sentence was a tragedy.

"Scooter is also a friend, and on a personal level [my wife] Lynne and I remain deeply saddened by this tragedy," he said in statement.

US District Judge Reggie B Walton said the evidence overwhelmingly proved Libby's guilt.

"People who occupy these types of positions, where they have the welfare and security of [the] nation in their hands, have a special obligation to not do anything that might create a problem," Judge Walton said in delivering the sentence.